Many different objects are utilized in electrical or automation systems in which it may be frequently desired to measure their temperature and/or resistivity. In some applications, a current is supplied through the objects for Joule heating. Often, the objects are in motion during operation due to various factors, including, but not limited to, property changes.
One such object is a shape memory alloy (SMA) wire that is increasingly being incorporated in such control devices as actuators, sensors, and the like. An SMA wire generally exhibits pseudo-elastic characteristics when it is cooled below a certain temperature at which a material crystal phase transformation occurs. In this phase, the wire will reversibly elongate under an applied stress. When heated above another temperature, the material also changes its crystal phase and contracts back to its original shape. It is often desirable to measure such properties as the temperature and/or the resistivity in order to monitor the crystal changes and to maximize their performance with this information.